The present invention generally relates to an agitator drive system for use in an automatic clothes washer, and more particularly relates to such a system embodying an alternately reversing drive motor.
Most commercially available top loading washing machines have an agitator that is connected to a reciprocating transmission driven unidirectionally by a motor. That is, the motor is typically a conventional constant speed, resistance-start induction motor that continuously drives the input shaft of the transmission in one direction, and in response thereto, the oscillating or periodic reversing transmission drives the tub mounted clothes agitator in one direction and then in the opposite direction. Although such transmissions are generally effective for their intended purpose of alternating the drive direction to provide back and forth agitator strokes, the transmissions are complicated mechanisms that are relatively expensive to manufacture.
A recent commercially available agitating clothes washer uses a reversing motor and a simple speed reducer to drive the agitator. Because the reversing action is provided by the motor itself, this system has the advantage of eliminating the need for an expensive and complex reciprocating transmission. The motor is a permanent split capacitor (PSC) motor that is substantially identical in size and material to the standard commonly used resistance-start induction motor of transmission drive washers, except that a run capacitor is required. This washer operates at about 20 agitation cycles or strokes per minute which is very low as compared to most transmission drive washers which may, for example, operate at 60 or more strokes per minute. Accordingly, the clothes may not be cleaned so well as with a higher stroke rate. Further, it has been found that when the stroke rate of this washer is increased two or three times (e.g. 40-60 strokes per minute) with a corresponding factor reduction in stroke angle, the motor operates above an acceptable operating temperature. Overheating apparently results because there are more start-ups at the higher stroke rate, and considerably more heat is generated in starting a motor than operating it at its running speed. As is well known, the operating temperature of a motor is closely associated with its life expectancy because deterioration of the wire insulation is a function of both time and temperature. Therefore, it would generally be unacceptable to operate the motor of this washer at a relatively high temperature. The operating temperature of the motor could be reduced by increasing the size of the motor or the copper in the windings, but such approaches would add considerably to the cost of the washer.